As implantable medical devices become smaller and smaller, and as more and more components are added to such devices, the real estate available for components is shrinking. Components too are shrinking in size, but the need for improving the use of available volume and space continues.
In implantable medical devices, the footprints of dice and stacked dice packages typically exceed the bottom die size. For example, when wire bonding is used to electrically connect a die to rigid or flexible interposers, the package size is much larger than the bottom die size, and is therefore very size inefficient.
One stacked die package in the industry uses a structure having a number of chips glued to one side of a substrate, and a connection array also laid out on the same side of the substrate. The chips are stacked by repeated hand-folding and adhering. This structure requires that perforations be placed along bend lines of the substrate to allow bending along precisely the correct lines. Further, each individual stacked package is cut individually once the substrate is folded.